I disagree. When flipped, the Clamshell calcs are very uncomfortable to hold in a hand due to the unergonomic sharp case edges and hollow back.
And the Clamshell calcs are wider on the back side than most other calcs, which is another disadvantage.
The Pioneers (HP-42S) and stretched Pioneers (HP-48) have a much more ergonomic case shape.

And the awful battery door construction of the original Clamshell calcs is extremely annoying every time you have to change batteries.

The redesigned case with battery door on the back side was one of the best things ACO (or how they were called then) made.

I agree with all your statements. I usually use the 28S flat on a desk but when I *have* to use it in hand it can be done. And, yes, the battery door is awful!

Also, Matt, remember when deciding to bypass the 48 series for the 28 that the 28 came first and is quite a bit less powerful than the later models. As far as I can tell you really only got one answer when you asked

Quote:
As the 48/49/50 series surpass and exceed the 28S/28C, what benefits does the 28 series merit?

and that was that the keyboard allowed more rapid entry in certain situations.

Ask how the 48 is superior and there are dozens (if not hundreds) of improvements. Starting with offline storage which sadly the 28 does not have.

Well, As I was browsing through the 28S Solution Books, it's quite revealing how many of those foundational routines are base code, functionality and algorithms in the 48/49/50G.

Perhaps in retrospect, it's very ambiguous. On the one hand, I can look at the 28 as foundational development for the beginnings of some very robust Symbolic Mathematics functionality in addition to introducing me to RPL--what I consider the pinnacle of RPN and calculator programming languages. On the other hand, my statement below is what I find so helpful in the 28S--an uncluttered keyboard versus the 50G's triple function keys.

Careful with that RPN/RPL comparison. They are very different beasts. There is little to no commonality between FOCAL (RPN's programming paradigm--at least on the 41) and RPL. At least that is how I see it.

RPL can be "keystroke programmed" in the sense that you can enter a series of instructions that get executed in-order as a program (I have made this argument before) but it is also a high-level structured programming language with a whole lot of power. I prefer FOCAL for simple tasks (and even sometimes more complex tasks simply because I am used to it) but RPL has a lot of power in more complex applications.

1-as I'm very fond of RPN, the 28/48/49/50 programming structure combines the postfix syntax with a structure of a programming language

2--Being both a calculator and computer programmer, the mathematics side gets more attention. So, having a calculator which I can program with a structured procedural language satisfies my challenge and helps to build up my proficiency for programming.

I have a low mileage 28C (stored without batteries) with the manuals and the box if you want to get your feet wet with the 28 series models. I regret selling my 41C setup years ago to get the 28C when it came out.